Study Of Acoustic Resources From Leakage Of Gas In Pipe And Acoustic Emission Signals Characteristics

For its low cost, high transportation velocity, and steady supply, pipe has being an essential conveyance on the transportation of streams such as petroleum, natural gas, living water, industry wastes, raw fuels, etc. And it has rated among railway, highway, third service, water carriage as one of the most essential means of transportation, being played important role in modern production and daily life. For the causes of corrosion, wear, man-made destroy, etc. leakage is a general failure type of pipe, which causes safety hazard to pipe transportation. Especially when the transport medium is flammable, poisonous, explosive, or harmful, the leakage of pipes will cause enormous loss and pollution of environment. So much attention is paid to the leakage testing of pipe in early stages.The paper mainly focuses on acoustic resources characteristics of leakage sources and propagation characteristics of acoustic waves along pipes, wave guide rods. Emphasis includes simulative analysis of leakage acoustic resource mechanism, characteristics research of leakage acoustic resources, propagation characteristics research of acoustic waves along pipes,experimental research of propagation process of acoustic emission signals along wave guide rods, experimental research of pipe leakage testing with wave guide rods.1.simulative research of leakage acoustic resource mechanismThe leakage of gas in pipes is a complex cascade process. Cascade flow field originated by leakage of gas in pipe is numerical simulated with infinite element software- Fluent. Flow field distribution and cascade velocity are gained. Also, through fitting, the distribution function of maximum leakage velocity is worked out when cascade leakage appears. On the basis of flow field analysis results, the relation is found between acoustic intensity and flow field parameters such as diameter of leakage hole, leakage inner pressure.2.Experimental research of leakage acoustic resources characteristicsIn order to research the characteristics of acoustic signals originated by leakage, experimental installation is erected in laboratory on leakage of gas in pressurized pipe. The emphasis is put on analysis of frequency domain of leakage acoustic signals, also the relation between leakage acoustic resource amplitude and internal pressure of pipe, diameter of leakage hole. After contrasting with numerical simulation results, the result shows that they are accordant.3.Propagation characteristics research of elastic wave along pipe excited by point sound sourceWhen point sound source is excited in pipe wall, transient stress wave will propagate along the pipe in the form of elastic wave. Through corresponding experimental research, some characteristics of elastic wave are advanced such as attenuation, wave velocity, and so on.4. Propagation characteristics research of elastic wave along pipe excited by continuous sound source Through experiments on leakage of gas in pressurized pipe and analysis of acoustic emission signals, some change rules are gained, including amplitude, energy, spectrum of AE signals changing with pressure, diameter of leakage hole, propagation distance. Also, the attenuation curve of amplitude of AE signals to propagation distance is advanced with the method of fitting.5.Testing research of leakage of gas in pipe with the aid of wave guide rodsTo leakage testing of pipes in special operating condition, wave guide rods are always needed. The length and diameter of wave guide rod specimens used in experiments are deferent. Length of them can be divided into three groups, and for diameter, the number are seven. Experiment results show that structure of wave guide rods has influence on AE waveforms and spectrums when the waves are excited by point sound sources, but for continuous sources, the influence is little.On the basis of erected experiment system for leakage testing of gas in pipe with the aid of wave guide rod, many experiments are carried out, after which, testing method is advanced. Also, AE signals characteristics under different pressure and different leakage diameter are discussed.